Colored aluminum pigments, process for producing them and their use

ABSTRACT

The invention concerns colored aluminum pigments comprising flake-form aluminum substrates which are coated with a metal oxide layer. The pigments are produced by a process which involves the steps of mixing a ground color pigment with a flake-form aluminum in the presence of a solvent. A metal acid ester is then added to the mixture and is then hydrolyzed to form a metal oxide layer on the aluminum substrate, followed by removal of the solvent and drying of the pigment. The pigments are useful as special-effect pigments in paints, lacquers, coatings, plastic materials, printing inks and cosmetic preparation.

BACKGROUND OF THE INVENTION

The invention concerns coloured aluminium pigments, a process for theproduction thereof and use thereof.

Aluminium pigments are used widely in coatings as special-effectpigments. The term special-effect pigments is used to denote pigmentswhich have a directed reflection at oriented, metallic or highlylight-refractive particles of a predominantly flat configuration (GermanStandard DIN 55944). They are always of plate-like or flake-likeconfiguration and have very large particle diameters compared with dyepigments. Their optical properties are determined by reflection andinterference. Depending on transparency, absorption, thickness,singlelayer or multi-layer structure, the special-effect pigmentsexhibit a metallic shine, a pearl shine, interference or interferencereflection. The main area of use are in the cosmetics and automobilesector, and in addition in colouring plastic materials, paints, leathercoatings, in the printing industry and in the ceramic industry. (For acomprehensive representation of the technical background, see W.Ostertag, Nachr. Chem. Techn. Lab. 1994, 9, 849.).

The special-effect pigments which are most frequently used are aluminiumflakes and coated mica flakes, wherein aluminium pigments exhibit atypical metal shine and coated mica flakes exhibit a typical pearlshine.

In recent years the need for coloured special-effect pigments hasincreased greatly. Therefore for example oxide-covered copper and brassflakes, substrates which are coated with transition metal oxides, suchas muscovite, phlogopite or glass, guanine single-crystals (fishsilver), BiOCl-single crystals, flake-form haematite single-crystals,flake-form phthalocyanines or crushed thin multi-layer films with aFabry-Perot-structure are used as special-effect pigments.

In order to achieve colour effects inter alia aluminium pigments arealso mixed with transparent dye pigments. The colouristic options withthat method are however limited insofar as it is not possible in thatway to achieve interference effects and therefore the pigments do nothave a pearl shine. However, because of the transparency, interferencepigments with a pearl shine, which are mostly based on coated micaflakes, have a poorer covering capability than aluminium pigments.Attempts have therefore been made to produce pigments with the goodcovering capability of aluminium flakes and the colouristic options ofinterference pigments, by colouring aluminium pigments.

U.S. Pat. No. 4,328,042 and EP-A-0 033 457 describe the production ofgold-coloured aluminium pigments by the deposition of iron oxide,wherein iron pentacarbonyl is oxidised with oxygen in a fluidised bed ofthe aluminium flakes, the bed being produced by fluidisation with inertgas. The disadvantage of that procedure is the very high level oftechnological expenditure.

U.S. Pat. No. 5,037,475 describes the production of aluminium pigmentswhich are coloured by fixing colour pigments on the metal surface. Thecolour pigments are fixed by way of carboxyl group-bearing polymers. Aprotective layer can be applied by polymerisation, to improve theadhesion. However the pigments produced in that way have only a lowlevel of colour intensity.

WO 91/04293 (PCT/US90/05236) describes the colouring of aluminiumpigments by fixing poly -coated colour pigments from aqueous solvents onthe metal surfaces by way of electrostatic forces. In that situation thecoating result depends in a complex manner on the type of aluminiumpigment, the nature of the polymer coating on the colour pigments, thesolvent composition and the pH-value.

EP-A-0 328 906 discloses titanium dioxide-coated metal pigments, interalia also aluminium pigments, which are produced by hydrolysis of anorganic titanate ester compound, for example tetraisopropoxytitanium, inthe presence of the metal flakes which are suspended in an organicmedium, at pH of from 4 to 8. Various colour shadescan be achieved withthat process by varying the thickness of the titanium dioxide layer.Maintaining specific conditions is crucial for producing the coatedpigments. The pH-value must be in the range of from 4 to 8 and thedropping speed used in adding the titanate ester must be in the range offrom 1.0×10⁻⁷ to 1.0×10⁻⁴ mole per minute and m² metal surface area.Therefore that process cannot be used on a large technical scale. Inaddition the coated pigments must be calcined after the drying operationin order to achieve colour effects as a suitable layer structure isachieved only by removal of the water from the metal oxide layer.Because of the low melting point of aluminium however the calcinationoperation can only be carried out with a very great deal of difficultywhen involving coated aluminium pigments.

U.S. Pat. No. 4,978,394 describes the production of titaniumdioxide-coated aluminium pigments by chemical vapour deposition (CVD),wherein titanium tetrachloride is reacted at a low level ofconcentration with water vapour in a fluidised bed in the presence ofhot aluminium particles. This process also suffers from the disadvantageof expensive technology.

U.S. Pat. No. 4,158,074 discloses the production of coloured aluminiumpigments by coating with a film comprising hydrated aluminium oxide andhydrated metal oxide. The film is produced by the treatment of finealuminium flakes or plates in an alkaline solution of an iron, nickel,cobalt, zinc or copper salt at elevated temperature at a pH-value offrom 8 to 12, that is to say by an electrochemical reaction of the metalsalts. In that way it is possible to produce gold-coloured pigments, andby the addition of chelating agents, also black-brown and grey-whitepigments.

U.S. Pat. No. 5,261,955 describes a sol-gel-process for the productionof coloured metal pigments, wherein the metal flakes or plates aredispersed in a sol of an inorganic salt, for example an aqueous alkalinezirconium oxide sol, the flakes or plates coated with the sol aredispersed after filtration in a solution of an inorganic compound, forexample cobalt nitrate, in an organic solvent, and a sol-gel layer isformed on the flakes by heating. The large number of individual stepsinvolved in that process means that a high level of apparatusexpenditure is also required.

JP-A-61-130375 discloses a gold-coloured aluminium pigment, produced bythe treatment of aluminium powder with dichrcmate, sodium fluoride andsurface-active agents in acid solution, drying and subsequent treatmentwith a fatty acid derivative. Colour shades other than gold cannot beachieved using this method.

German laid-open application (DE-OS) No 41 40 295 describes pigmentscomprising carrier materials in flake or plate form, preferably mica,which are coated with an inorganic matrix containing metal oxides and/ordye particles in the sub-micrometre range. The operation of coating thesubstrates is effected out of acid aqueous suspensions by the hydrolysisof metal salts, preferably titanium tetrachloride, in the presence ofmetal oxide and/or dye particles. However it is not possible to colouraluminium flakes using that process because under those conditions thealuminium particles quickly break down.

U.S. Pat. No. 3,067,052 discloses coloured aluminium particles which areproduced by the oxidation of aluminium powder with KMnO₄ -solution,possibly with the addition of a reducing agent. The colour shade ofthose pigments is golden, possibly also with a greenish or reddishshade, depending on the respective reducing agent used.

DE 25 57 796 discloses a coloured aluminium pigment which is coated witha metal oxide layer containing carbon black as the colour pigment. Theproportion of colour pigment is 10% by weight at a maximum. According tothat specification, larger amounts of colour pigment have a detrimentaleffect on shine and colour.

DE 36 17 430 discloses coated coloured pigments, the base pigmentcomprising mica. Coatings containing colour pigment are not named inthat document. The colour effects of the described pigments are producedby interference.

DE 42 23 383 describes metal sulphide-coated substrates, wherein themetal sulphide layer does not contain any colour pigments.

DE 42 23 384 (U.S. Pat. No. 5,374,306) discloses metal oxide-coatedaluminium substrates without a colour pigment component. According tothat publication, the lowest possible content of carbon, that is to saylubricants and organic impurities, is decisive in regard to achievinggood shine effects. The substrates must therefore be pre-treated byheating in an oxygen-bearing atmosphere.

JP-1-110 568 (Patent Abstracts of Japan, Section C, Volume 13 (1989) No331 (C-622)) discloses aluminium substrates coated with thin oxidelayers, without a colour pigment component, the colour effects thereofbeing produced by interference.

For the stated reasons, the processes for the production of colouredpigments on a mica basis cannot be used to produce aluminium pigments,in respect of which however there is a high level of interest because ofthe higher covering capability and the metal shine. The known processesfor colouring aluminium pigments however afford only few colour shades,predominantly in the gold range, and for the major part are veryexpensive in terms of apparatus. Therefore there was still a need foraluminium pigments which are coloured in different colour shades, and aneed for a process which is simple in terms of apparatus, for theproduction of those coloured aluminium pigments.

SUMMARY OF THE INVENTION

The object of the present invention is to provide such pigments and aprocess for the production thereof.

That object is attained by the provision of aluminium pigmentscomprising aluminium substrates in flake or lamellar form, which arecoated with a coloured pigment-bearing metal oxide layer. The pigmentsaccording to the invention are produced from flake-form aluminiumsubstrates by the metal oxide layer being produced not by precipitationof the metal salts from an aqueous solution, but by the controlledhydrolysis of metal acid esters in the presence of colour pigments in anorganic solvent by means of a sol-gel process which is carried out inone step. The aluminium pigments according to the invention present avery wide range of different colour shades, thus for example blue, red,violet and gold, and a metallic shine.

In the pigment according to the invention the amount of colour pigmentis from 15 to 40% by weight, preferably at least 20% by weight and theamount of metal oxide is preferably from 3 to 95% by weight, in eachcase with respect to the aluminium substrate.

An embodiment of the invention concerns coloured aluminium pigmentswhich are obtainable by a procedure whereby:

a) one or more types of colour pigments is ground in the usual manner,

b) the ground material is mixed with aluminium pigments and one or moreorganic solvents,

c) one or more metal acid esters is added,

d) 1 to 5 times the amount of water which is stoichiometricallynecessary for complete hydrolysis of the metal acid esters is added,

e) after the end of the reaction the volatile constituents are removedfrom the mixture in the usual manner, and

f) the pigments obtained are dried.

In a preferred embodiment the aluminium pigments are not subjected to adegreasing treatment before step b) is performed.

In a further/preferred embodiment a part of the metal acid ester isalready added to the colour pigment or pigments in step a) during thegrinding operation, and the amount of metal acid ester iscorrespondingly reduced in step c).

In a further embodiment step a) involves the addition of a usualadditive which improves pigment dispersion.

Besides the pigments themselves the invention also concerns a processfor the production thereof, including above-mentioned steps a) to f).

In a further embodiment of the process according to the invention thereaction mixture obtained in step d) is heated to a temperature ofbetween 40° C. and the boiling point of the solvent added in step b)and/or a basic catalyst is added.

The drying operation in step f) is preferably effected at less than 200°C., still more preferably at less than 150° C., and most desirably atless than 100° C., in a vacuum, for example at 90° C. in a vacuum dryingcabinet.

DETAILED DESCRIPTION OF THE INVENTION

The colour pigments that can be used are conventional organic andinorganic colour pigments. Preferably those colour pigments which have ahigh level of transparency and colour-fastness are used. The man skilledin the art can direct himself to the literature (for example G. Buxbaum,Industrial Inorganic Pigments, VCH-Verlag, Weinheim, 1993 and W. Herbst,K. Hunger, Industrielle Organische Pigmente, VCH-Verlag, Weinheim, 1987)and to manufacturer recommendations. Preferred colour pigments are forexample C.I. Pigment Blue 15:3, C.I. Pigment Red 179, C.I. Pigment Red101 and C.I. Pigment Red 202. It is possible to use a single type ofpigment or a mixture of a plurality of types of pigments, depending onthe respective desired colour shade of the aluminium pigment accordingto the invention. The color pigments are not in the form of a layer ofcarbon, metal and/or metal oxide.

The operation of grinding the colour pigments is effected in the usualmanner, for example in a bead mill or in a grinding-body mill, forexample with zirconium oxide balls. The grinding operation can beeffected in a part of the metal acid ester or in a conventional solvent,for example white spirit. Simultaneous use/of white spirit or othersolvent and metal acid ester in the grinding operation is also possible.It is also possible to add an additive for improving pigmentdispersibility such as for example Antiterra U 80, from Byk-Chemie.

Suitable aluminium pigments in step c) are all conventional aluminiumpigments which can be used for decorative coatings. Round aluminiumflakes or plates (so-called silver dollars) are preferably used.Particularly preferred is Stapa Metallux of the 2000 type series (fromEckart). Because of their low scatter component those silver dollarspermit particularly brilliant colouring effects.

The solvents involved in step b) are organic solvents, preferablywater-miscible solvents. Particularly preferred are alcohols such asmethanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol andt-butanol, most preferably i-propanol.

It is also possible, according to the respective needs, after step d) ofthe process, prior to the end of the reaction, to again add anadditional amount of the solvent used in step b). The total amount ofthe solvent added is preferably from 150 to 300 ml, with respect to 100g of aluminium substrate.

Suitable metal acid esters are selected from the group comprising alkyland aryl alcoholates, carboxylates, alkyl alcoholates or carboxylates,substituted with carboxyl residues or alkyl residues or aryl residues,of titanium, zirconium, silicon, aluminium and boron. Particularlypreferred are alkyl and aryl alcoholates, in particular C₁ -C₆ alkylalcoholates such as methanolates, ethanolates, n-propanolates,i-propanolates, n-butanolates, i-butanolates and t-butanolates of thestated metals. These compounds have the general formula M(OR)_(y),wherein M is titanium, zirconium, vanadium, silicon, aluminium or boron,R is a C₁ -C₆ alkyl, phenyl, xylyl, tolyl or cresyl group, and y is 3 or4. This type of compound can also be considered as an ester of the metalacids, for example ortho-silicic acid, boric acid, aluminium hydroxide,titanic acid or zirconic acid. Preferably aluminiumtriisopropylate(triisopropylaluminate), titanium tetraisopropylate(tetraisopropyltitanate), polymeric n-butyltitanate, titaniumtetraisobutylate (tetraisobutyltitanate), zirconium tetraisopropylate(tetraisopropylzirconate), o-silicic acid tetraethyl ester(tetraethylorthosilicate) and triethylborate (boric acid triethylester)are used. Mixed alcoholates are also possible, that is to say not allresidues OR are the same.

In addition it is preferably possible to use acetyl acetonates,acetoacytylacetonates, possibly also substituted by alkyl or alkenylresidues, or acetoacetates of the stated metals. Mixedalcoholates/acetylacetonates, alcoholates/acetoacetylacetonates oralcoholates/acetoacetates, that is to say those metal acid esters whichcontain both alcoholate residues and also acetylacetonate residues,acetoacetylacetonates or acetoacetate residues are also suitable.Preferred examples of that type of metal acid esters are zirconium,aluminium or titanium acetylacetonate (Zr(acac)₄, Ti(acac)₄ orAl(acac)₃) and diisobutyloleylacetoacetylaluminate ordiisopropyloleylacetoacetylacetonate. In addition it is also possible touse mixtures of metal acid esters of different metals which can also bepartially condensed, for exaple Dynasil^(R) (fran Huls), a mixedAl--Si-metal acid ester.

An amount of 15 to 40 g of colour pigment, preferably from20 to 40 g,and from 0.1 to 0.8 mole of metal acid ester, preferably 0.5 mole, areused relative to 100 g of aluminium substrate with a surface area ofabout 4 m² /g (BET). When using more than 0.8 mole of metal acid ester,that gives a coloured aluminium pigment with a poor shine and thepigments have a tendency to undesired agglomeration. When using lessthan 0.1 mole of metal acid ester, the stability of the coated pigmentin relation to water and acids is not adequate and it is not possible toachieve adequate adhesion of the colour pigments on the aluminiumpigments. If less colour pigment than 15 g is used, the result achievedis an inadequate colour effect, while if more than 40 g of colourpigment is used, the metal shine of the aluminium pigments isexcessively greatly covered over.

The crucial consideration for the process according to the invention isthe amount of water used in step d), which is from 1 to 5 times theamount necessary for complete hydrolysis of the metal acid ester. Agreater excess of water can result in greying of the aluminium pigmentsand is therefore to be avoided. Therefore 4 to 20 moles of water,preferably from 4.5 to 10 moles, are used in relation to 1 mole of atetravalent metal acid ester, for example an ortho-silicate, titanate orzironate. Accordingly, from 3 to 15 moles of water, preferably from 3.1to 8 moles, are used in relation to 1 mole of a trivalent metal acidester, for example a borate or aluminate. Preferably water from whichall salt has been removed is used.

The reaction is conducted at a temperature from ambient temperature upto the boiling point of the solvent or solvents. The temperature dependson the reactivity of the metal acid esters and is adjusted according torequirements.

Particularly when using silicic acid esters, the addition of basiccatalysts is preferred, which can be added in step d). It is possible touse the usual basic catalysts. Suitable bases are for example aminessuch as triethylamine, ethylene diamine or tributyl amine or substitutedamines such as dimethylethanolamine or methoxypropylamine. In additionit is also possible to add aminosilanes which have an auto-catalyticeffect, for example 3-aminopropyl- trimethoxysilane,N-aminoethyl-3-aminopropyltrimethoxysilane or3,4,5-dihydroimidazol-1-yl-propyltriethoxysilane. A further addition ofbase may possibly be effected once again, after some time.

After termination of the reaction, that is to say generally after from0.5 to 10 hours, the volatile constituents are removed from the reactionmixture in the usual way, for example by distillation or by beingpressed out. The pigments are then dried, for example in a vacuum dryingcabinet.

The coloured aluminium pigments can be subjected to further processinglike conventional aluminium pigments. For example, for many areas ofuse, it is advantageous to produce non-dusting pastes by the addition ofsolvents such as hydrocarbons, ethyl acetate, methoxypropanol orbutylglycol.

The production process according to the invention for coloured aluminiumpigments provides that the metal acid ester is hydrolysed and thencondensed, while finally metal oxides are formed in a sol-gel process,which metal oxides are deposited on the aluminium flakes in the form ofa dense closed coating and in that case simultaneously fix the colourpigments on the metal surface. The hydrolysis/condensation proceduretakes place in a highly complex manner, the beginning of the reactionchain can be represented by the following equations for alcoholate-metalacid ester:

    M(OR).sub.y +H.sub.2 O→(RO).sub.y-l --M--OH+ROH     (1)

    2(RO).sub.y-l --M--OH→(RO).sub.y-l --M--O--M--(OR).sub.y-l (2)

One function of the metal oxide layer lies in providing as an "adhesive"for a strongly adhesive bond between the metal pigment and the colourpigment. A further function of the metal oxide layer is to protect thealuminium pigment from moisture and chemicals. The coloured aluminiumpigments according to the invention can therefore be used for exampleboth in conventional solvent-bearing paints and lacquers and also inwater-base paints and lacquers.

The novel coloured aluminium pigments according to the invention haveparticularly great brilliance and a wide spectrum in respect of possiblecolour shades. The pigments are highly stable. The process is simple tocarry out even on a large technical scale and does not require expensiveequipment. There is no need for calcination of the pigments as thepigments according to the invention already exhibit excellentbrilliance, colour intensity and stability after the drying operation.

The pigments according to the invention can advantageously be used forproviding special effects in paints and lacquers, coatings, plasticmaterials, printing inks and cosmetic preparations.

THE INVENTION IS DESCRIBED IN GREATER DETAIL HEREINAFTER BY MEANS OFEXAMPLES. EXAMPLE 1

30 g of C.I. Pigment Blue 15:3 is dispersed and ground with 85 g ofsilicic acid tetraethylester (from Wacker) by means of 300 g zirconiumoxide balls (0.7 mm diameter) in a grinding body mill (Red Devil, fromthe company Union N.J. USA). 100 g of aluminium pigment (Stapa Metallux2154, BET surface area 3.8 m² /g, from the company Eckart) and 208 ml ofisopropanol are added to that dispersion at ambient temperature, and themixture is stirred for 1 hour. After that a solution of 0.78 g ofethylene diamine and 51.4 g of water from which all salt has beenremoved is added and the suspension is heated with stirring at 80° C. Atintervals each of 1 hour, 0.78 g of ethylene diamine and 51.4 g ofisopropanol are also added twice. The mixture is heated for a total of 6hours. The product is then filtered off and dried at 90° C. in a vacuumcabinet. That gives a metallically shiny, intensively blue aluminiumpigment.

Colour pigment: about 19%, S_(i) O₂ : about 15%; Aluminium pigment:about 65%.

EXAMPLE 2

20 g of C.I. Pigment Red 179 is ground with 56.7 g of silicic acidtetraethylester, 23.3 g of white spirit and 11.4 g of a wetting anddispersing additive (Antiterra U 80, from Byk-Chemie), using theprocedure from Example 1. 100 g of aluminium pigment (Stapa Metallux2154) and 208 ml of isopropanol are added to the mixture. After 0.5hours of stirring at ambient temperature, 28.3 g of silicic acidtetraethylester is added. After a further 0.5 hour, a solution of 0.78 gof ethylene diamine and 51.4 g of water from which all salt has beenremoved is added and heated to 80° C. At intervals of 1 hour, 0.78 g ofethylene diamine and 51.4 g of isopropanol are also added twice. Afterheating for 6 hours the mixture is filtered off and dried at 90° C. in avacuum cabinet. The result obtained is a metallically shiny, dark-redaluminium pigment.

Colour pigment: about 15%; S_(i) O₂ : about 17%; Aluminium content:about 69%.

EXAMPLE 3

30 g of C.I. Pigment Blue 15:3 is crushed in 85 g of white spirit inaccordance with Example 1. 100 g of aluminium pigment (Stapa Metallux2154, from Eckart) and 208 ml of isopropanol are added thereto bymixing. After 0.5 hour 85 g of silicic acid tetraethylester is added.After a further 0.5 hour, after the addition of a solution of 0.78 g ofethylene diamine in 51.4 g of water from which all salt has beenremoved, heating to 80° C. is effected. After 2 hours 0.78 g of ethylenediamine and 51.4 g of isopropanol are added. After heating for 6 hoursthe mixture is filtered off and dried at 90° C. in the vacuum cabinet.The result obtained is a blue, metallically shiny aluminium pigment.

Colour pigment: about 19%; S_(i) O₂ : about 15%; Aluminium content:about 65%.

EXAMPLE 4

40 g of C.I. Pigment Red 101 is ground in 90 g of isopropanol, as inExample 1. The further procedure corresponds to that of Example 3. Thealuminium pigment used is STAPA Metallux 8154 from Eckart Werke. Theresult obtained is a metallically shiny, gold aluminium pigment.

Colour pigment: about 24%; S_(i) O₂ : about 14% Aluminium content: about61%.

EXAMPLES 5 to 8

In Examples 5 to 8 dispersion of the respective colour pigment iseffected as described in Example 3. Colouring is also effected asdescribed in Example 3 with the metal acid esters stated in Table 1 andthe amounts of water listed in Table 1.

                  TABLE 1    ______________________________________           Example 5                   Example 6 Example 7 Example 8    ______________________________________    Colour pigment             Pigment Red                       Pigment Red                                 Pigment Red                                         Pigment Red    C.I.     202       179       202     202    Metal acid             Zirconium Boric acid                                 Diisobutyl-                                         Titanium    ester (85 g             acetyl    triethylester                                 oleylaceto-                                         (IV)isopro-    in each case)             acetonate ALDRICH   acetylalu-                                         pylate    Supplier ALDRICH             minate  KENRICH                                 KENRICH    Amount of             48        32.4      34.3    26.7    watering    Coloured Metallically                       Metallically                                 Metallically                                         Metallically    aluminium             shiny     shiny     shiny   shiny    pigment  red-violet                       red       red-violet                                         red-violet    Composition:    Colour pigment             19.60%    16.20%    18.50%  18.10%    Metal oxide             11.4% ZrO.sub.2                       21.2% B.sub.2 O.sub.3                                 9.3% Al.sub.2 O.sub.3                                         13.5% TiO.sub.2    Aluminium             69%       62.30%    71.20%  67.40%    ______________________________________

We claim:
 1. A colored aluminum pigment comprising a flake-form aluminumsubstrate coated with a single layer of metal oxide derived from a metalacid ester wherein the layer of the metal oxide contains at least onecolor pigment, not including carbon, metal and/or metal oxide, saidcolor pigment selected from the group consisting of an organic colorpigment, an inorganic color pigment, and a mixture of more than onecolor pigment present in the oxide layer in an amount of from 15 to 40%by weight with respect to the aluminum substrate.
 2. A colored aluminumpigment according to claim 1 wherein the amount of metal oxide in thelayer is from 3 to 95% by weight with respect to the aluminum substrate.3. A colored aluminum pigment according to claim 1 wherein the colorpigment is present in the metal oxide layer in an amount of at least 20%by weight with respect to the aluminum substrate.
 4. A colored aluminumpigment according to claim 1 wherein said at least one color pigment isan organic color pigment.
 5. A product selected from the groupconsisting of paints, lacquers, coatings, printing inks, plasticmaterials, and cosmetic preparations containing an amount of the coloredaluminum pigment of claim 1 sufficient to impart a metallic shine, tothe product.
 6. A colored aluminum pigment prepared according to theprocess comprising the steps of:a) grinding at least one color pigment,selected from the group consisting of an organic color pigment, aninorganic color pigment and a mixture of more than one of said colorpigments, but not including carbon, metal and/or metal oxide, b) forminga mix of the ground color pigment with an aluminum pigment in thepresence of a water miscible organic solvent, c) adding at least onemetal acid ester to the mix, d) hydrolyzing the metal acid ester byaddition to the mix of from 1 to 5 times the amount of water which isstoichiometrically necessary for complete hydrolysis of the metal acidester, e) at the end of the hydrolysis reaction, removing the organicsolvent and other volatile constituents from the reaction mixture, andf) drying the resultant aluminum pigment.
 7. A colored aluminum pigmentaccording to claim 6 wherein the ground color pigment is mixed with thealuminum pigment and organic solvent without prior degreasing of thealuminum pigment.
 8. A colored aluminum pigment according to claim 6further including the addition of a portion of the total amount of metalacid ester in step a) with the remainder of the acid ester being addedin step c).
 9. A colored aluminum pigment according to claim 6 furtherincluding the addition of a pigment dispersant during the grinding step.10. A colored aluminum pigment according to claim 6 wherein from 15 to40 gms. of color pigment and a total of from 0.1 to 0.8 moles of metalacid ester are mixed with 100 gms. of aluminum pigment.
 11. A coloredaluminum pigment according to claim 6 wherein the metal acid estercomprises at least one ester selected from the group consisting of alkylalcoholates, aryl alcoholates, carboxylates, alcoholates andcarboxylates substituted with carboxyl residues, alkyl residues or arylresidues, of titanium, zirconium, vanadium, silicon, aluminum boron, andmixed condensed metal acid esters of said metals.
 12. A colored aluminumpigment according to claim 6 wherein the metal acid ester is selectedfrom the group consisting of triisopropylaluminate,tetraisopropyltitanate, tetraisobutyltitanate, polymericn-butyltitanate, tetraisopropylzirconate, tetraethylorthosilicate,triethylborate, aluminum acetylacetonate, titanium acetylacetonate,zirconium acetylacetonate, diisobutyloleylacetoacetylaluminate,diisopropyloleylacetoacetylacetonate and mixed Si--Al metal acid esters.13. A colored aluminum pigment according to claim 6 wherein the mixobtained in step d) is heated to a temperature of from 40 degrees C. tothe boiling point of the solvent to remove the solvent and othervolatile constituents from the mixture.
 14. A colored aluminum pigmentaccording to claim 6 wherein a basic acid catalyst is added to thereaction mixture in step d) followed by removal of the organic solventand other volatile constituents from the reaction mixture.
 15. A coloredaluminum pigment according to claim 6 wherein drying is effected in stepf) at a temperature of less than 200 degrees C.
 16. A colored aluminumpigment according to claim 6 wherein drying is effected in step f) at atemperature of less than about 100 degrees C. in a vacuum.
 17. A productselected from the group consisting of paints, lacquers, coatings,printing inks, plastic materials, and cosmetic preparations containingan amount of the colored aluminum pigment of claim 6 sufficient toimpart a metallic shine to the product.
 18. A process for preparing acolored aluminum pigment comprising the steps of:a) grinding at leastone color pigment selected from the group consisting of an organic colorpigment, an inorganic color pigment, and a mixture of more than one ofsaid color pigments, but not including carbon, metal and/or metaloxides, b) forming a mix of the ground color pigment with an aluminumpigment in the presence of a water miscible organic solvent, c) adding ametal acid ester to the mix, d) hydrolyzing the metal acid ester byaddition to the mix of from 1 to 5 times the amount of water which isstoichiometrically necessary for complete hydrolysis of the metal acidester, e) at the end of the hydrolysis reaction, removing the organicsolvent and the other volatile constituents from the reaction mixture,and f) drying the resultant aluminum pigment.
 19. The process accordingto claim 18 wherein the ground color pigment is mixed with the aluminumpigment and organic solvent without prior degreasing of the aluminumpigment.
 20. The process according to claim 18 further including theaddition of a portion of metal acid ester in step a) with the remainderof the acid ester being added in step c).
 21. The process according toclaim 18 further including the addition of a pigment dispersant duringthe grinding step.
 22. The process according to claim 18 wherein from 15to 40 gms of color pigment and a total of from 0.1 to 0.8 moles of metalacid ester are added relative to 100 gms of aluminum pigment.
 23. Theprocess according to claim 18 wherein the metal acid ester comprises atleast one ester of a metal selected from the group consisting of alkylalcoholates, aryl alcoholates, carboxylates, alcoholates andcarboxylates substituted with carboxyl residues, alkyl residues oftitanium, zirconium, vanadium, silicon, aluminum and boron, and mixedcondensed metal acid esters of said metals.
 24. The process according toclaim 18 wherein the metal acid ester is selected from the groupconsisting of triisopropylaluminate, tetraisopropyltitanate,tetraisobutyltitanate, polymeric n-butytitanate, tetraisoproplzirconate,tetraethylorthosilicate, triethylborate, aluminum acetylacetonate,titanium acetylacetonate, zirconium acetylacetonate,diisobutyloleylacetoacetylaluminate,diisopropyloleylacetoacetylacetonate and mixed Si--Al metal acid esters.25. The process according to claim 18 wherein the metal acid which ishydrolized in step d) is heated to a temperature of from 40 degrees C.to the boiling point of the solvent to remove the solvent and othervolatile constituents from the mixture.
 26. The process according toclaim 18 including the step of adding a basic acid catalyst to the mixduring hydrolysis of the metal acid ester.
 27. The process according toclaim 18 wherein drying is effected in step f) at a temperature of lessthan 200 degrees C.
 28. The process according to claim 18 wherein dryingis effected in step c) at a temperature of less than about 100 degreesC. in a vacuum.